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The Effect of Contralateral Signal on Distortion Product Otoacoustic Emissions and Psychophysical Tuning Curves at 1 and 2 kHz

100%
Wicher A.
Acta Physica Polonica A
|
2013
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vol. 123
|
issue 6
1001-1006
EN
The main aim of this work was to determine the influence of contralateral stimulation (CS) on the psychophysical tuning curves (PTCs) and distortion product otoacoustic emissions (DPOAEs). PTCs and DPOAEs were measured in two modes: in the presence or absence of CS. The contralateral signal was a wideband noise (bandwidth 0.2-10 kHz) at a level of 50 dB sound pressure level (SPL). The primary tones (F_1 and F_2) were presented at levels of L_1=60 dB SPL, and L_2=50 dB SPL. The signal frequency used in the measurements of the PTC was 1 kHz or 2 kHz. For both PTC signal frequencies the CS significantly reduces the sharpness of the PTCs. The average change in level of DPOAE under the influence of CS throughout the whole range of frequencies takes an effect of suppression. The CS has a significant effect on decreasing the value of the quality factor (Q_{10Roex}) of PTCs (F(1,9)= 19.36, p=0.002). The CS caused a decrease in the level of DPOAE in 88% of cases. The maximum suppression of the DPOAE level occurs for the F_2 frequency from 1 kHz to 2 kHz.
2
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Masking a Frequency Band in a Musical Fragment Played by a Single Instrument

80%
Kleczkowski P., Plewa M., Pluta M.
Acta Physica Polonica A
|
2011
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vol. 119
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issue 6A
991-995
EN
The phenomenon of masking in the environment of musical sounds has not yet been deeply investigated. An experiment was conducted to find out whether masking of a band of frequencies in a musical instrument sound by the remaining spectral content of that instrument could be explained by "energetic" masking, i.e. masking resulting from overlapping patterns of excitation on the basilar membrane. An isolated, about one octave wide, band of frequencies of the saxophone sound playing a couple of notes legato was masked alternatively by two maskers: CBN - the band of noise occupying the same frequency range plus the remaining spectral content of the saxophone sound, and BN - the same band of noise acting alone. For both maskers, the level of noise was increased gradually to detect the respective thresholds of masking. Masker CBN was more efficient in masking by about 15 dB, indicating that the harmonics below and above the analysed band contributed substantially more to masking than noise inside the band. As energetic masking of those harmonics was weak, non-energetic or "informational" masking prevailed.
3
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Psychoacoustical Estimation of Selected Acoustic Signals Which Can Be Applied at Pedestrian Crosswalks

80%
Bogusz E., Furmann A.
Acta Physica Polonica A
|
2011
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vol. 119
|
issue 6A
925-931
EN
The paper presents a psychoacoustical evaluation of selected acoustic signals, which according to Polish and international recommendations can be applied at pedestrian crosswalks. The aim of the study was the optimal adjustment of parameters of the signals emitted at pedestrian crosswalks, and to meet the expectations of persons with vision impairments as well as nearby residents or workers working near the crossing. The psychoacoustical evaluation of acoustic signals consists of determination of the hearing threshold of signals in the quiet, detection of signals presented against a background of various types of traffic noises (estimated signal-to-noise ratio) and annoyance assessment of signals. Three types of intermittent sounds were analysed: signals with rectangular time pattern filled up with rectangular wave, signals with rectangular time pattern filled up with sinusoidal wave and signals with triangular time pattern filled up with sinusoidal wave. Four fundamental frequencies (550 Hz, 880 Hz, 1580 Hz and 2000 Hz) and two repetition rates (5 Hz and 9 Hz) were tested. The results of the study have shown that the most suitable signals which can be applied at pedestrian crosswalks are the intermittent sounds with rectangular time pattern filled up with rectangular wave of fundamental frequencies 880 Hz and 1580 Hz and repetition rate 5 Hz and the intermittent sounds with rectangular time pattern and triangular time pattern both filled up with sinusoidal wave of fundamental frequencies 1580 Hz and repetition rate 5 Hz.
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